    Patent Document 1: JP09-237770A    Patent Document 2: JP11-214336A1    Patent Document 3: JP11-233461A
In these years, demands for solar cells are rapidly increasing because of a growing awareness of energy problems such as exhaustion of fossil fuel sources and environmental problems such as global warming.
In these demands, for silicon possibly to be the cells for solar batteries, such high purity silicon is demanded that the purity is 99.9999% or more and the resistivity is 0.5 Ω·cm or more, and off-specification products have been used for raw materials, which are produced in fabricating high purity silicon used in semiconductor industries, or in fabricating substrates for IC, LSI, etc.
However, particularly in the solar cell, because a single solar cell module is fabricated using about 54 rectangular silicon wafers with a five-inch side, the used amount is more enormous than the used amount of silicon wafers for IC, LSI, or the like, high purity silicon for semiconductors is expensive, and the yield of off-specification products is small, causing a problem in that there is a limit to the amount of silicon materials supplied for the solar cell.
In addition, problems have not arisen so far because the yield of off-specification products of electronic device silicon exceeds the demand of the solar cell. However, the demand of the solar cell is exceeding the yield of off-specification products of electronic device silicon today, causing a serious problem of shortage of raw materials for solar cell silicon.
On the other hand, because the solar cell silicon wafer with a rough surface can surely provide the surface area, the surfaces of wafers, which are single wafers after a silicon ingot is sliced with a wire-saw, are not polished in mirror finish like semiconductor wafers.
Thus, in the fabrication process of the semiconductor wafer, a large-sized, expensive separation and transfer apparatus is used to carry single wafers to a machine for the subsequent process step (surface finishing process or the like). However, the real situation in the fabrication process of the solar cell wafer was that wafers are manually separated one by one without using an expensive, large-sized separation and transfer apparatus, which affects product costs as well.
On the other hand, in consideration of the above-mentioned problems of shortage of raw materials for solar cell silicon, raw material costs, or the like, the solar cell wafer is also being reduced in thickness like the semiconductor wafer, and manual one by one separation in the fabrication process of the solar cell wafer tends to cause breakage or the like. Because of this, there is an increasing demand for small-sized, inexpensive separation apparatuses.
Now, a large number of wafers, which are sliced from an ingot formed in an almost cylindrical shape and attached to a support plate using a wire-saw, are pre-washed in a pre-washing device as the wafers are in a cylindrical pack attached to the support plate in order to remove slurry, cutting dust, or the like. After the pre-washed wafers are removed from the support plate using a removing device in order to remove the wafers from the support plate for single wafers, the wafers are separated into individual wafers in a separation and transfer apparatus, and then carried to the subsequent process step.
At this time, ultrasonic cleaning techniques are known in which slurry, cutting dust, or the like attached to wafers is removed with air bubbles generated by a pre-washing device (for example, see Patent Documents 1 to 3).
Although ultrasonic washing is effective for washing the side surfaces and two end surfaces of the silicon ingot, there is a problem in that it is difficult to cause a washing fluid to reach the back of the space between the sliced wafers, and slurry, cutting dust, or the like attached to the wafer surface cannot be completely removed, resulting in degraded washing effect.
Then, in removing the pre-washed wafers from the support plate using the removing device (single wafer separation), they are immersed in a liquid solution such as acetic acid or the like for removing the wafers from the support plate and they are simultaneously subjected to secondary washing for removing remaining slurry, cutting dust, etc.
However, the individual single wafers after secondary washing are in intimate contact with each other in a horizontally stacked state (piled state) when carried, so that there is a problem in that it is difficult to reliably perform separating operations because the initial resistance for separating a stationary wafer at the topmost position from a wafer therebelow (directly therebelow) is static frictional resistance greater than dynamic frictional resistance.
Then, in the above-mentioned Patent Document 1, there is disclosed that two jet nozzles that blow water upward are provided in the inner lower part of a chuter in a separation and transfer apparatus, pressure water is spouted from the jet nozzles through the space between the chuter and stacked wafers, and this causes the topmost wafer to be slightly lifted by the spouted pressure water when the topmost wafer is carried to the top side of the chuter for performing smooth wafer separating operations because the adhesion between the topmost wafer and the wafer directly therebelow is reduced.